(A) Field of the Invention
This invention relates generally to a benthic screen for controlling aquatic plant growth typically found near shoreline areas of lakes, ponds, rivers and similar bodies of water.
(B) Description of the Prior Art
The growth of aquatic plants and vegetation in near-shore areas, i.e. in areas less than 200 feet from shore or in water less than 6 feet deep, has rendered many beach, shoreline and coastline areas unsuitable for swimming, boating or other recreational water activities. Typical unwanted growth includes seaweed, lake weed, Eurasian watermilfoil, hydrilla, curly leaf pond weed, duck weed, coontail, elodea, naiad, water lilies and the like. Physical, mechanical as well as chemical methods have been utilized to control the unwanted growth. Typical physical and mechanical control methods include hand pulling, cutting with a water weed cutter or an electric mower, raking, suction and aeration. Chemical control methods involve the use of herbicides and dyes. Some of these methods are described in “The Conesus Lake Dockside Near-Shore Lake Weed & Algae Treatment Guide” (2002 Edition) by The Conesus Lake Association, Inc. There are significant disadvantages associated with each of these methods. These disadvantages are particularly applicable to shoreline residents in that they are either expensive, labor intensive, environmentally unsuitable, time consuming or inefficient.
One of the more practical and effective methods for controlling aquatic plant growth has been the use of benthic screens or barriers which cover a portion of the bottom surface or bed of a body of water in near-shore areas. Such screens have been found to be particularly suitable for use by shoreline residents for the purpose of controlling aquatic growth in small or localized areas such as areas used for docking, swimming or other recreational activities. The screens usually consist of a sheet of plastic or cloth material that is placed over a specific area to remove plant growth. The structure of a typical screen as described in the Conesus Guide includes a 12-foot by 12-foot wooden frame with a screening material such as burlap, a woven synthetic or a geotextile attached to the frame. The screen is anchored at the bottom of a body of water with four sandbags. The disadvantages in use of the screen are limited material durability, the requirement for a separate anchoring system, screen movement caused by water movements or gas accumulation under the screen and the bulky and cumbersome nature of the structure. The report also describes an “alternate frame approach” which may be used in place of a frame that is constructed from four 2×2's. The alternate frame includes four pieces of aluminum conduit or PVC piping filled with sand. While the alternate frame eliminates the need for a separate anchoring system, it does not provide any means for accumulated gases to escape. Also, because of the rigidity of the frame structure, the screen remains bulky and therefore cumbersome to handle.
U.S. Pat. No. 4,056,936 to Mayer discloses a benthic screen that is made from a porous fiberglass material. The material's porosity permits moving water to pass through the screen rather than causing the whole screen to move. The position of the screen is thereby stabilized. Stakes are used to secure the corners of the screen to the bed. Because the screen is porous, it transmits more light than a screen with lower porosity. The increased light allows plants to grow for a longer period of time before their demise. Also, the stakes pose a potential hazard to watercraft and can become dislodged by the movement of water or contact with a foreign object.
U.S. Pat. No. 4,577,996 to Elias et al discloses a benthic barrier which comprises a fabric coated on at least one side with silicone rubber thick enough to prevent root penetration and thin enough to allow gases formed below the barrier to pass through the coating and escape. The barrier is anchored with rocks and stakes. While the barrier effectively shades out light, it is subject to dislodgement if the anchoring stakes or rocks are displaced.
U.S. Pat. No. 4,518,280 to Fletcher discloses an aquatic weed barrier which comprises a film having a plurality of incisions therein and having a light transmittance of less than 50%. The incisions provide means for the escape of gases which may collect under the film from decomposing plants. The film is held in position with rocks. While the film kills most of the weeds, some weeds are able to survive by growing through the incisions. The use of rocks as an anchoring means is disadvantageous for the reasons previously described.
It is therefore an object of this invention to provide a benthic screen which effectively controls the growth of aquatic plants and vegetation.
It is a further object of this invention to provide a benthic screen having an opacity sufficient to reduce light penetration below the threshold point required for aquatic plant survival.
It is another object of this invention to provide a benthic screen which effectively vents gases produced by decomposing plants under the screen.
It is yet another object of this invention to provide a benthic screen which has anchoring means which are an integral part of the screen.
It is a further object of this invention to provide a benthic screen that is readily transportable, easily installed and conveniently stored by one or two persons.